Magnetic pick ups



United States Patent'O MAGNETIC PICK UPS Rudolph Dopera and Edward E. Dopera, both of 124 Concert St., El Monte, Calif.

Filed Sept. 8, 1959, Ser. No. 838,717 17 Claims. (Cl. 84-115) This invention pertains to new and improved magnetic pick ups for stringed musical instruments and to stringed musical instruments in which such pick ups are incorporated.

Stringed instruments have conventionally been constructed so that the volume of sound produced by such instruments is dependent upon the inherent construction of these instruments. Unfortunately many common instruments are incapable of producing a sufi'icient volume of sound on many occasions. Thus, for example, a conventional violin may literally be drowned out so that it cannot be heard at a dance because of various ambient sounds. in order to increase the volume of sound produced by stringed instruments a number of different types of pick up devices have been proposed for use with such instruments. These pick up devices are generally connected to an appropriate amplifier and speaker used to increase the volume of sound produced to a desired level.

As virtually anyone who is familiar with stringed instruments knows quality of tone is extremely important with such instruments. A number of amplifiers and speakers capable of faithfully reproducing sound are, of course, known. Unfortunately the prior pick up devices used with stringed instruments to provide an input signal into such amplifiers have not been capable of faithfully conveying the sound of such instruments to such amplifiers as an electrical signal in such a way that the amplified sounds produced have the desired qualities. A pick up for use with a stringed musical instrument cannot be a conventional microphone type of construction, since such devices would tend to feed back into the amplifier various unwanted ambient sounds. Hence, a satisfactory pick up to use with a stringed musical instrument must be incorporated within the instrument itself so as to be sensitive only to vibrations within such an instrument.

A broad object of the present invention is to provide new and improved magnetic pick ups for use with various types of stringed musical instruments. Thus, an object of the invention is to provide magnetic pick ups for use with various known types of instruments such as guitars, violins, cellos, bass viols, ukuleles, mandolins, and the like. Another closely related object of this invention is to provide magnetic pick ups which can be used with instruments using various types of strings, such as gut strings, hexamethyldiamine-adapic acid polymer strings, metal strings and the like.

A more important object of the present invention is to provide magnetic pick ups for use in conveying input electrical signals to amplifiers, which pick ups in use give extremely faithful and accurate tonal reproduction, regardless of the instruments upon which they are employed. Another corresponding object of this invention is to provide magnetic pick ups which give a comparatively soft, muted or milder tone than various prior related devices of a similar character. Still further objects of this invention are to provide magnetic pick upset the type described, which may be either sold separately or sold as an integral part of stringed instruments, which are relatively inexpensive to manufacture, which may be easily installed in stringed instruments either during the manufacture of such instruments, or after, and which are capable of rendering extremely satisfactory performance 1n use.

These and other objects of this invention, as well as many advantages of it, will be more fully apparent from a consideration of the remainder of this description including the appended claims and the accompanying drawing in which:

Fig. l is a top plan view of a violin incorporating a magnetic pick up of this invention as an integral part of this violin;

Fig. 2 is a cross-sectional view on an enlarged scale taken at line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view taken at line 3-3 of Fig. 2; and

Fig. 4 is a view similar to Fig. 2 of a part of a modified magnetic pick up of this invention.

The accompanying drawing is primarily intended so as to clearly illustrate several presently preferred embodiments or forms of this invention. Those skilled in the art to which this invention pertains will realize that the precise physical shapes of the various parts of the magnetic pick ups illustrated are of a secondary character, and are not directly indicative of principles involved in the construction of magnetic pick ups as herein described. They will further realize that the basic features of this invention as set forth in the appended claims can be embodied within other differently appearing pick up structures.

As an aid to understanding this invention it can be stated in essentially summary form that it concerns magnetic pick ups, each of which is designed to be used on a stringed instrument and is formed so as to include fixed and movable bridges. These bridges are secured to one another so that the movable bridge is capable of transmitting vibrations from strings resting against it so as to cause relative movement between a permanent magnet and an armature holding a pick up coil. During the use of a pick up of this invention such relative movement causes a change in an electrical value in accordance with the tones produced by the instrument upon which the pick up is used.

The actual nature of this invention is best more fully described or explained by referring directly to the accompanying drawing. In the drawing there is shown a pick up 10 of the present invention installed upon a top 12 of a generally conventionally appearing violin 14. It is to be understood that the pick up 10 may be installed upon virtually any other type of stringed instrument in substantially the same location as this pick up is installed upon the violin 14.

The violin 14 includes a body 16 of which the top 12 forms a part. From this body 16 there extends in a conventional manner a neck 18 having at its end remote from the body 16 a plurality of keys 20. A number of strings 22 extend from these keys 20 along the neck 18 and generally across the top 12 so that their ends remote from the keys 20 are held by a tail-piece 24 secured to the body 16 in a known manner. With the violin 14 the entire body 16 acts as a resonating chamber; various openings 26 may be located within the top 12 in the conventional manner.

The pick up 10 includes a plate 28 of hard rubber or other similar material secured to the top 12 by means of screws 30 so as to generally cover an opening 32 in this top. 0n the plate 28 there are formed brackets 34 which extend through the opening 32 generally into the interior of the body 16. These brackets are secured .3. through the use of screws 36 to small, Il-shaped, nonmagnetic braces 38. Both these two braces 38 are secured by means of a rivet 40 to an armature 42 formed out of soft iron or various other equivalent magnetically, permeable materials. The armature 42 includes ends 44 extending so as to terminate generally in the same plane as the top 12 of the body 16. Around the center portion of the armature 42 there is located a conventional wire coil 46 which is connected through wires 48 to a volume control 50 of known type mounted upon the top 12. This volume control 50 is similarly connected to a plug 52 which can be employed in connecting the pick up It to a suitable amplifier or speaker (not shown) of a known type.

The plate 28 is formed so as to include a generally U-shaped notch 54 facing away from the top 12. This notch carries a plate-like fixed bridge 56formed out of wood or other similar material so that the bridge 56 extends from the top 12 m shown in Figs. 2 and 3 of the drawing. The bridge 56 includes an edge 58 located transverse to the neck 18, which edge 58 carries the strings 22 in the conventional manner.

This fixed bridge 56 is secured to a similar movable bridge 60 through the use of a threaded bolt 62. The movable bridge 60 extends in a plane parallel to the fixed bridge 56; it also includes an edge 64, corresponding to the edge 58, which edge 64 also supports the strings 22. The bolt 62 connecting the bridges 56 and 60 is preferably located at about the physical centers of these bridges so as to be spaced between the edges 58 and 64 of them and the plate 23.

A small, curved brace 65 is held at its ends by one of the screws 3% and by the bolt 62 so as to support the bridge 56 in an upright position at all times. This brace 65 is preferably formed out of a strip of resilient spring steel or other equivalent materials so as to accomplish this supporting function while simultaneously permitting some vibration of the bridge 56 as the violin 14 is played in order to obtain optimum sound reproduction. With the pick up 1b a rigid metal tube 66 is held under compression between the bridges 56 and 60 by means of the bolt 62. This tube 66 extends around this bolt 62; it serves to assist the bolt 62 in supporting or holding the movable bridge 6% with respect to the fixed bridge 56.

The bridge 69 terminates in an attached block 68 located remote from the edge 64 generally in the same plane as the top 12. As can be seen in Figs. 2 and 3 of the drawing this block 68 extends within an opening 70 in the plate 28 and is located immediately above the ends 44 of the armature 42. The block 68 carries an elongated bar magnet 72, the ends of which are located adjacent to the ends 44 of the armature 42, but which are spaced from these ends 44. The block 68 and the movable bridge 60 attached to it are in part supported in this position by means of resilient coil springs 74 which, as shown in Fig. 3, are located in pairs of cavities 76 formed in the brackets 34 and in this block 68 so that one of cacti of the cavities 76 is located directly opposite to another of these cavities.

In order to obtain the desired reproduction of sound with the pick up it is preferred to locate at the'ends of the springs 74 within the cavities 76 small elastomeric pads 73 formed out of rubber or other similar material. For the same reason it is also preferred to form the springs 74 out of metal and to coat these springs with rubber or other equivalent materials. Both of these expedients aid in obtaining a desired muted efiect during the use of a pick up it and aid in softening or mellowing the tone produced with this pick up 10, although, of course, these results are achieved in a large degree even without the use of these expedients.

From the aforegoing it will be seen that in the violin 14 the bridges 56 and 60 are held in place by the tension normally applied to the strings v22. With this structure the fixed bridge 56 is located immediately adjacent to the tailpiece 24, and the movable bridge 60 is located on the side of the fixed bridge 56 where the normal operations in playing the violin are performed. With this construction the edges 58 and 64 are spaced from the top 12 in substantially the same amount, with the edge 64 extending slightly beyond the edge 58. As a result of this construction the principal forces applied to the bridges 56 and 60 are applied to the bridge 56 while only a comparatively restricted amount of force is applied to the movable bridge 60. The forces applied to this movable bridge 60 are sufficient to hold it in place at all times and to hold the springs 74 under compression. If desired, a small guard '80 may be located on the plate 28 by means of screws 82 so as to prevent movement of the block 68 and the attached bridge 60 away from this plate 28 when the strings 22 are removed. This guard also protects against unwanted movement caused by direct physical contact.

The pick up 16), of course, comes into operation when it is appropriately connected to an amplifier and speaker (not shown) as indicated in the preceding discussion, and when the violin 14 is played in the conventional manner. During such use of the violin 14 vibrations of the strings 22 will cause a corresponding movement or vibration of the movable bridge 60, moving the magnet 72 with respect to the armature 42, causing a change in an electrical value in an established manner. Because of the method in which the pick up 10 is constructed, such changes in an electrical value will correspond faithfully to the actual character of the sounds produced with this instrument.

In Fig. 4 of the drawing there is shown a modified pick up of the present invention which is essentially the same as the pick up 10 except in one respect. For convenience the various parts of the pick up 90 which are identical to corresponding parts of the pick up 10 are designated in the drawing and in this description by the primes of the numerals previously employed, and are not separately described.

in the pick up 90 the tube 66 previously described is omitted and in its place a small coil spring 92 is located under compression between the bridges 56 and 60. If desired, the spring 92 may be coated with rubber or other similar material of elastomeric character so as to aid in obtaining accurate sound reproduction. This spring 92 is considered advantageous in many cases inasmuch as it provides adequate support for the movable bridge 60', preventing unwanted bending of this bridge, while simultaneously allowing this bridge 60 to vibrate in a desired manner in accordance with the vibrations of the strings (not shown) used in connection with it.

In both the pick ups 10 and 90 the manner in which vibrations are transmitted from the strings employed is considered quite important in obtaining satisfactory tonal reproduction. If desired, it is possible to modify the pick :ups 10 and 90 so that the magnet employed is rigidly mounted in place upon a plate such as the plate 28 or upon the top of an instrument and so that the'armature and coil used is secured to the movable bridge 60 so as to be movable withrespect to such a rigidly mounted magnet, although this is not preferred inasmuch as it adds to the weight of the movable bridge used, and hence, tends to afiect its sensitivity to vibration. It will be realized from the aforegoing description that, if desired, the plate 28 as a separate element may be dispensed with, and that the top of a musical instrument of virtually any type may be formed so as to serve the same purpose or function as this plate.

Because of the nature of this invention it is to be considered as being limited only by the appended claims forming a part of this disclosure.

We claim:

1. A magnetic pick up for a stringed instrument which includes: a plate adapted to be attached to a stringed instrument; a fixed bridge extending from said plate; a

movable bridge extending parallel to said fixed bridge away from said plate; spring means held between said movable bridge and said plate; holding means securing said movable and said fixed bridges to one another; armature means located on said plate, said armature means having ends located adjacent to said movable bridge; pick up coil means located around said armature means; and permanent magnet means located on said movable bridge adjacent to said ends of said armature means.

2. A stringed instrument which includes: an instrument top; a fixed bridge extending from said top; a movable bridge extending parallel to said fixed bridge from said top; holding means securing said movable and said fixed bridges to one another; spring means located between said movable bridge and said top; armature means located on said top, said armature means having ends located adjacent to said movable bridge; pick up coil means located around said armature means; permanent magnet means located on said movable bridge adjacent to said ends of said armature means; and string means held under tension so as to extend across said top, said string means being held so as to exert force against said fixed bridge and said movable bridge.

3. A stringed musical instrument which comprises: a hollow body having a top, said body serving as a resonating chamber; neck means extending from said body; key means located on the extremity of said neck means remote from said body; tailpiece means located on said top of said body in alignment with said neck means; a plate positioned on said top of said body; a fixed bridge located on said plate so as to extend from said top of said body, said bridge being located transverse to said neck means and having an edge located away from said body; a movable bridge located parallel to said fixed bridge on the side thereof adjacent tosaid neck means, said movable bridge having an edge spaced further from said top than said fixed bridge; spring means positioned between said movable bridge and said plate; holding means located between said plate and said edges of said bridges rigidly securing said bridges to one another; armature means mounted on said pla.e, said armature means including ends located adjacent to said movable bridge; pick up coil means located around said armature means; permanent magnet means located on said movable bridge, said permanent magnet means including ends adjacent to said ends of said armature means; and string means held under tension by said tailpiece means and said key means, said string means extending across said edges of said bridges so as to hold said bridges under compression with respect to said body.

4. A stringed musical instrument as defined in claim 3 wherein said body includes an opening formed therein and wherein said plate means covers said opening and wherein said armature means and said pick up coil means are located Within said body.

5. A stringed musical instrument as defined in claim 3 wherein said movable bridge and said plate includes pairs of cavities located opposite one another and wherein said spring means comprise coil springs located so as to extend into exposed cavities on said movable bridge and said plate.

6. A stringed musical instrument as defined in claim 3 wherein said spring means comprises coil springs, each of said coil springs being formed of metal coated with an elastomeric material.

7. A stringed musical instrument as defined in claim 3 wherein said plate includes notch means formed thereon and wherein said fixed bridge extends into said notch means and is held therein by said string means.

8. A stringed musical instrument as defined in claim 3 wherein said holding means includes a member attached to said bridges and coil spring means held under compression between said bridges, said coil spring means extending around said member.

9. A stringed musical instrument as defined in claim 3 wherein said holding means includes a member attached to said bridges and a tube contacting said bridges, said tube extending around said member.

10. A magnetic pick up for a stringed musical instrument which includes: a plate adapted to be attached to a stringed instrument, said plate having a notch extending from one side thereof and having an opening formed therethrough adjacent to said notch; a fixed bridge positioned within said notch so as to extend from said plate; a movable bridge located parallel to said fixed bridge so as to extend from said plate, said movable plate terminating within said opening in said plate; a member securing the center portions of said bridges to one another; spring means located between said movable bridge and said plate; permanent magnet means located on the portion of said movable bridge adjacent to said plate within said opening; armature means mounted on said plate on the side thereof remote from said bridges, said armature means having ends located adjacent to said permanent magnet means; and pick up coil means located around said armature means.

11. A magnetic pick up as defined in claim 10 wherein said spring means comprises coil spring, each of said coil sprinsg being formed of metal coated with an elastomeric material.

12. A magnetic pick up as defined in claim 10 including resilient pad means located between said spring means and said movable bridge.

13. A magnetic pick up for a stringed musical instrument which includes: a plate adapted to be attached to a stringed instrument; a fixed bridge extending from said plate; a movable bridge extending from said plate parallel to said fixed bridge; holding means securing said bridges together; resilient means held between said plate and said movable bridge; and co-acting means for chang ing an electrical value mounted on said plate and said movable bridge.

14. A magnetic pick up as defined in claim 13 Wherein said co-acting means comprises armature means surrounded by coil means and permanent magnet means located adjacent to said armature means and wherein movement of said movable bridge causes relative movement between said armature means and said permanent magnet means.

15. A magnetic pick up for a stringed musical instrument which includes: a plate adapted to be attached to a stringed instrument; a fixed bridge positioned in said plate so as to extend from said plate; brace means attached to said fixed bridge and said plate for supporting said fixed bridge on said plate; a movable bridge extending from said plate parallel to said fixed bridge; holding means attached to said bridges for holding said bridges with respect to one another; resilient means held between said movable bridge and said plate; a co-acting means for changing an electrical value mounted on said plate and said movable bridge.

16. A magnetic pick up as defined in claim 15 wherein said brace means comprises a strip of resilient material attached to said fixed bridge and said plate.

17. A magnetic pick up as defined in claim 16 wherein said plate includes a notch formed thereon, and wherein said fixed bridge is positioned so as to extend from said notch.

References Cited in the file of this patent UNITED STATES PATENTS 215,023 Sexton May 6, 1879 466,501 Lyon Jan. 5, 1892 2,171,430 Kislingbury Aug. 29, 1939 2,486,647 Harker Nov. 1, 1949 FOREIGN PATENTS 686,683 France Apr. 15, 1930 986,949 France Apr. 11, 1951 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 978,945 p April 11, 1961 Rudolph Dopera et 31.

It is hereby certified "that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 6O for "exposed" read opposed column 6, line 23, for "spring", second occurrence read 1-:- sprlngs line 24 for "sprinsg" read springs Signed and sealed this 12th day of September 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC column 6, line 23, for "spring" second occurrence read "UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N09 2978 945 I p April 11 1961 Rudolph Dopera et 31.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should. read as corrected below.

Column 5 line 6O for "exposed" read opposed 7:" springs line 24 for "sprinsg" read springs Signed and sealed this 12th day of September 1961m (SEAL) Attest:

" ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

